Out of all the criticism I've read of Salinger's work, I've found this to be one of the most helpful. Essentially it provides a good overview of the various religious traditions referenced by the Glass clan. The author does a good job not only of relating the context of religion within the story, but also gives a nice concise overview of the religions by themselves (in fact, the presentation rather reminds me of Steele's Guidebook to Zen and the Art of Motorcycle Maintenance). Overall, I think this book is a great way to get some bearing on various religions, especially if your're thinking about taking a class. (often books about religions are rather disembodied, so seeing how the Glass Family interacts with various ideas is a vivid place to start)